(87)Rb versus (133)Cs in cold atom fountains: a comparison

Area of Science:

• Atomic Physics
• Metrology
• Quantum Information Science

Background:

• Accurate atomic clocks are crucial for fundamental physics tests and modern technologies.
• Laser cooling techniques have significantly advanced the precision of atomic frequency standards.

Purpose of the Study:

• To present a new measurement of the ground state hyperfine frequency of laser-cooled Rubidium-87 (Rb).
• To evaluate the frequency shift due to cold collisions in Rb atomic clocks.
• To test for possible variations in the fine structure constant by comparing Rb and Cs atomic fountains.

Main Methods:

• Operation of a laser-cooled Rubidium-87 (Rb) atomic frequency standard.
• Comparison of the Rb standard with a primary Cesium (Cs) fountain standard.
• Analysis of cold collision effects on the Rb hyperfine frequency.
• Intercomparison of Rb and Cs cold atom fountains to probe for variations in fundamental constants.

Main Results:

• A new measurement of the Rb-87 ground state hyperfine frequency: 6 834 682 610.904 333(17) Hz with a relative accuracy of 2.4x10(-15).
• The frequency shift induced by cold collisions was evaluated as Deltanu/nu(Rb)=(-7.2+/-20)x10(-24) n.
• The measurement is compatible with zero and significantly smaller than for Cesium (Cs).
• A test for variations in the fine structure constant yielded a limit of 2.7x10(-14) yr(-1).

Conclusions:

• The presented Rb-87 frequency standard achieves high accuracy, enabling precise measurements.
• Cold collision effects in Rb clocks are quantified and found to be small.
• The comparison between Rb and Cs fountains provides stringent limits on variations of fundamental constants.